49 3
I mean, FRRR or FLLL or FLFLLF could return us to the base,
it also doesn't violate any of two rules:
1. The total number of letters F must not exceed S and 2. the total number of letters L and R must not exceed T

are there any more restrictions???

The problem asks: "What is the longest closed path that you can assemble?"

Your examples are not closed loops. The first and last squares, although they are neighbours, they don't match their path endings.