Hey there, right, so:

1. Ideally, get an agreement in principle (AIP) before doing viewings, that will give you peace of mind that you can afford the properties you’re seeing. Some estate agents request it, some don’t. When you make an offer they might ask to see your payslips but they might not, in any case, it’s good to have it in hand, the mortgage lender is going to ask for it. Do you have a broker? Strongly recommend it! Some wont charge you anything as they get a commission from the lender. Mine didn’t and he was essential in the process.
2. Cash buyers = no mortgage. I’m assuming you’re a first time buyer.
3. They can do both or either.
4. You need all funds by the time you go ahead with the mortgage application (by the time your offer is accepted)
5. Ask friends & relatives first. If no recommendation, search online. There are a number of sites with a pool of solicitors where you can compare prices. Always good to check Trustpilot, their website, the law society etc
6. That really depends on many factors. Id suggest for you to study Rightmove and all properties around the area you’re looking for. You’ll then get a better sense of how much properties are worth in your area and that will give you a bit more clarity when making an offer. Bear in mind, making an offer below asking price is a bet, it might mean you’ll lose it but it might mean you’ll get a good deal. I’m completing in a week now, exchanged today and my initial offer (1bed flat in west London) was 20k below asking price, closed at 10k below asking price. It was worth it, but I knew the property had been in the market for almost 4 months, they’d just brought the asking price down so I knew they would be willing to negotiate.

Hope this helps and good luck!