Cgt

I bought a house 4 years ago and lived in this for 1 year, I then went abroad and rented this out. After one year i came back to the coutnry and rented an apartment for just under a year, i then bought a second house and moved into this full time. No stamp duty was required as it was under the limit.
The first property is still rented out,
however, i am thinking of now renting this 2nd property out and moving back into my first house.
Is there any implications on this ?

Also, If i decide to sell my 1st property in 12 months time after living in that for 12 months will i have to pay any Capital gains tax ?