hi Jewel. Welcome to the forum

Regarding your questions, I'll just answer the ones that I know I'm sure the experts here can answer you.

Q1: 1. Is it more difficult applying tourist visa if your boyfriend who is sponsoring your visit haven't been visited you first?
-I think it will be because you will need to show proofs of your relationship and one of the requirements is meeting in person.

Q2: Is it a big question if you have a relative living in UK and not the one sponsoring your visit?
-I think they will assume it as one of the reason why you will not come back because you have a relative there

Q4: 3. Is a Guarantee Letter from my boyfriend enough to prove that i will be back home before the visa expires, since i do not have any property nor savings?
-please refer to this from UKBA site
Can you act as a guarantor for your visitor?
You cannot guarantee that the visitor who you are sponsoring will leave at the end of their visit. If we decide that your visitor cannot enter the UK, this does not mean that we doubt what you have told us. It is because the visitor has not satisfied us that they qualify for entry.
http://www.ukba.homeoffice.gov.uk/vi...tor/documents/

Q4: 4. What documents my boyfriend should provide since he is self employed?
-I'll let them answer that because I don't know.


Please correct me if I'm wrong