Should I sell BTC to invest it? 
No.You don't sell your bitcoin to invest into an ICO. If you want to invest into an ICO, use a part of your savings (not in btc) so that you keep both of them. Because if you really think that it's a good project.
You don't have to sacrifice your bitcoin for it. That's my opinion and that's what I'm going to do. I'll keep my bitcoin and will use cash to invest on any project/ICO. But isn't it that ICOs are almost forgotten these days?
When I sold BTC to participate in the ITO of Shirld DAO, I realized that it can only invest up to 1000USDT
but this could be better than ico . the only disadvantage of them is that you cant invest higher amounts but isnt it great ?
because they are controlling the risk and you can only loose small if ever the project didnt go well but profit would still be better if they became a success because more people will invest eventually .