This is not the case now with a lot of policy's now days, the cheaper provides removed this to lower cost as it classed as high risk.
I know of someone who was caught out by this as his policy's from years ago had it and drove his son car assuming he was covered.
read this
https://www.moneysupermarket.com/motorbike-insurance/third-party-fire-theft/
Third party is covering other people, their cars/ bikes / street furniture (lamp post, hedges, etc), if you damage them.
Theft + fire - adds cover if it stolen or catches fire.
comprehensive - term is lose but covers you bike and you, but read your policy cover.
Note on cars for youngsters TPFAT seem to cost more than full comprehensive.