Good question, you have a number of questions all rolled in one. The best thing is to ring Landlord Advice UK (if you are a BLA member, if not join for FREE) they will explain it to you very well, they are the tenant experts.
British Landlords Association - The BLA, is a national landlords association, for residential landlords & letting agents. Members have several benefits in joining a national landlords association. Members have free access, to our helpline and access to documents, to download. We campaign for a better, fair, a viable, buy to let housing market. We aim to train, equip and support landlords, throughout the UK. The association helpline, for members during COVID-19, is open 7 days. The British Landlords Association is a free UK organisation. Landlords in England, Wales & Scotland are welcome to join the BLA.