For lvl 5 frienship you have 5 extra tries per week- example: if you join TI on monday with lvl5+ friends then you can do up to 10 rewarding tries. Then you will have just the 15 normal tries to use untill the end of week.

So, overall: 20 normal tries + 5 friendship ones per week. And there's limit of 5 normal rewarding tries every day, even when you have more chances to use, but those 5 friendship tries doesn't count to that limit. And like I said- 5 friendship tries per week only.

What I mean by saturday/sunday is that if you will have some tries left from weekend, normal or frienship ones- you still can do it on weekend, you don't have to do all of them untill thursday, but keep in mind that limit of 5 rewarding ones each day.