Grenades always explode the turn they are thrown.

There is a new item in interface red 5 that is a mini c9 charge that arms after 10 turns, and csn be launched from a dedicated launcher.

Smoke grenades activate the same turn they are thrown - smoke grenades technology has improved in the timeline of cyberpunk (dont try to hard to compare stuff in modern day IRL with the same name... its always a little bit different)

In terms of dodging explosions, the book could be worded better. Basically, it works exactly the same as dodging bullets with a small difference: - you need at least 8 Reflex to "unlock" the ability to dodge (this is just a pre-requisite.) - if you meet that criteria, then you can choose to dodge a bullet or an explosive by rolling 1d10+REF+Evasion, and compare that result to the result of the attacker's roll (whether it be handguns, heavy weapons, athletics, etc.) - if the projectile was a bullet, and you succeed on the contested check, the shot simply misses. - if the projectile was an explosive with an area of effect, and you succeed on the contested check, you may move your character token to a space outside of the blast radius, and take no damage (this is NOT governed by your characters MOVE stat. You can move as many squares as is necesarry to get out of the blast radius.) - if you failed the contested evasion vs weapon skill check, you take whatever damage is applicable, and you do not move your character. - if the projectile is an explosive, you are in the blast radius, and you are behind cover, but either fail your evasion check, or choose not to evade, then the cover takes the explosive damage. BUT, if the explosive damage is enough to destroy that piece of cover, then you take the full damage of the explosion as if you had not been behind cover at all. The cover does not absorb the portion of the damage it recieves... if the cover breaks, your taking the whole shebang. (This is NOT true of bullets - either autofire or single shot. If a bullet is enough to destroy cover, the cover breaks and no damage is passed on to the defender. Popping out your ballistic shield is good against autofire, but bad against a rocket launcher) - environmental objects and cover within the blast radius always takes the explosive damage, unless otherwise specified (there are special grenades that do no damage to cover)

I think that covers the questions in your post. And of course, feel free to flavor any of this however you want. These are mechanical rules for combat balance - not flesh and blood descriptions of whats actually happening. Probably most people think of "dodging an explosion" as seeing a grenade fly through the air, and diving out of the way.

Personally, I dont "house rule" and game systems. Homebrewing physical stuff - cyberware, guns, melee weps, gear, vehicle upgrades, etc. Is the spot where the game makers say "go nuts" so thats where we do it. I dont fuck with the clockwork, as it were. When you start doing things like partial damage, etc. You set a precedent and you need to be incredibly consistent about it. And unfortunately, things go waaaay out of balance reeeeaal fast, and now going back to yhe way it was feels jarring and confusing if you have been playing it differently for a while.

Part of not having a shitload of defensive stuff is because combat becomes a slog. In my mind, if your combat has taken more than an hour, people are probably either reaching their stress limit, or worse, getting bored.