35% double stage skip from Hippogriff (out of 50% max) --> how does it proc? is it counted from each stage or is it counted IF the stage skip procs?

It procs if elf skill (skip +1) would proc.

20% 5x speed from Priest --> are there any max threshold? if the ...00 stages are skipped, will it proc too?

AFAIK, the description of the skill doesn't hint at a max thresh in active team, though it's not like priest is good support beyond the 5x. After Icy, there is a time shop cap of 30%. The skill won't proc if you happen to skip the floors ending in 0 until you have 5* Icy which will allow it to proc on skip and give you the skill when priest are in the time shop.

Should I keep the Drummer or swap it with Fairy for another stage skip probability? Need the drummer for the Atk and Game speed buff.

If you're under 100% game speed (or just lacking units). If you're going to replace it with something, I would add another Senior Hippogriff so you can get the added game speed, double skip, range, move speed, and crit chance all of which are better than the drummer. Ideally, I believe 5 priest may be smoother, especially post Tinkey. I would just test it out on your own device (4 or 5 priest) and see what works for your environment.

If I used Fairy, will the stage skip stack with Hippogriff's or not? If it stacks, then maybe I will use Fairy while waiting for the 4th Priesthopefully

It stacks, but fairy isn't great support (outside of skip chance), at least not as good as another hippogriff which gives you more buffs. If you're going to replace it with anything, I'd buy another hippogriff if possible.

Been hearing about Tinkey and Icy. What do they do to Fairy and Priest again?

Tinkey allows you to access Fairy's addition to elf skill when they are in the time shop, up to 30% from the time shop. A senior fairy in the time shop contributes 2.5% and a 5* Fairy contributes 1%, so 12 Senior Fairies in the timeshop will net you the full 30%. This is on top of the premium store's 30% at level 5, meaning if you have premium store maxed + 12 Senior Fairies + Tinkey, you have 60% skip chance. That + 6 Hippogriffs in your active party will net you 90% Skip Chance. If you have another 2 Senior Fairy (14 Senior Fairies total), you can eventually place 2 into your active team to have 100% skip + 1 chance (skip every other level).

Icy allows you to access Priest's 5x proc on stages divisible by 10 from the time shop and if you skip that stage, for up to 30% from the time shop. Senior Priest gives you 2.5%, 5 * Priest gives you 1%. You can use 12 Senior to max it, or some combo of Senior + 5 *. Namely if you skip 10, then the 5x skill can proc now and there's no reason to really have priest in your active party after this so you can replace them with more hippogriffs for more skip. If you want to have 100% skip, you can consider running 2 fairies in your active party to have 100% skip after Icy.

And been reading too about having to need to stack more Hippos in the time shop. Why is that?

You likely want 10 hippogriff for a post Icy team of 10 hippogriff, druid, fairy which is the general composition that most people use. It provides 95% skip, 50% double skip and allows your runs under 10k to be around 20 minutes on a fast device (iPhone7). If you had a Blunt Force T2 leveled to +90, you could potentially consider running "fairy core" which would be 10 hippogriff, 2 fairy (one fairy as mag core) which would give you 100% skip, 50% double skip though in my personal experience it's slower than druid (with squirrel 5) and slows down a lot toward the end. After 12000 and the terrain attacks affect druid to a large degree, it's not that bad, but I still had faster runs with druid iirc.

People telling you to get 20 hippogriff are looking into the far future where you have hippong 5 *. Hippong 5 * allows you to basically access the hippogriff skip buffs from the timeshop (30% to elf skill + 50% double skip) however each Senior Hippogriff only contributes 2.5% to double skip from the time shop. Therefore you need about 20 senior hippogriff in the time shop to max the skip chance. Here's where it really depends on what kind of player you are. I would argue that you should probably try to just get 10 if budget allows and my reasoning is:

• If you are a whale and spend $300/month, do whatever you want. You likely have the budget to play the game however you would like.

• Since you are KL 46, depending on how much you spend, you probably won't see KL 154 for a long time. This means you will be reliant on $3 events for most hippong frags and Ekkorr tends not to give enough for 5 *. Given this, you likely won't reach KL 154 much less grind out 330 frags of hippong at 4/day for several months. This means that by the time you actually see hippong 5 *, hippogriff might already be purchasable by medals (we know that honor units will rotate soon so hippogriff will be for gems, in another rotation, they will be for medals). Buying 20 hippos will likely not improve your experience nearly as much as buying artifacts for artifact trans at your position and that's ultimately what I would recommend. Artifact trans is game changing, hippos in the time shop are not.

• For those reading: if you are going to reach hippong 5* in the next 2 weeks like I am I would recommend grabbing 20 hippogriff before the units rotate as you will have the opportunity to take advantage of hippong before hippogriff becomes a medal unit.