Tax question

Tax Planning and Financial

Question 1:

If I were to buy a property for £100000 of which I put a deposit of £20000 down (£80000 would be made up of a mortgage (BTL)) then: -

If in 10 years time the propery is worth £150000 and I decide to sell then am I right in saying that I will be subject to CGT on £150000 - £100000 = £50000?

So I would effectively get my £20000 deposit back for 'free'?

Also if not trading under a company and as a sole trader I would have to pay 40% of the profit minus my CGT allowence for that year (approx £10000)
So 40% of £40000 = £16000?

Why can't I roll on previous years CGT that I may not have used?

Question 2:

If I had the same property as described above but decided to move in for 6 months prior to selling it I'm aware I can clain PPR. Therefore getting tax relief;

Does this apply for all of the gains made on the property for the last 10 years?

Any replies appreciated.