GPU UEFI/Legacy Bios support question

[furiousTaher]

1a. Graphics card vendor websites have bios support information- Legacy or UEFI or both. What does that actually mean? I think I know what UEFI and Legacy(epic blue screen) bios are. 

does the graphics card also depend on which type of bios I have? 
Is this really important? I didn't see too many posts about it, just couple of questions on tomshardware.
Why Some GPU supports only UEFI, some only Legacy and some both?

for example- sapphire r9 nano only supports legacy bios according to website. r9 fury x supports only legacy and fury only supports uefi bios

 

1b. If its important then why evga or asus websites didn't mention bios support?

 

1c. Is there any backward compatibility thingy here?

 

1d. If I have a old legacy bios p55+ core i7 .... or... amd old motherboard with phenom x6, will it support sapphire r9 nano(legacy) or r9 fury (uefi)?

 

2a. If a motherboard has UEFI bios(and has a pciE16x) will it be able to run any graphics card which has UEFI support? 

2b. (same question goes for legacy).
2c. If a GPU says that it supports both UEFI and Legacy will it run properly on any mobo (with x16 slot)?
2d. Does this support ability also depends on operating system? if so then let me know some details about windows7/8/10 graphics card support.

 

 

3.  r9 280x sapphire or many other radeon device has a dual bios switch, what does it do, does it have to do anything with UEFI/Legacy support? or is only for overclock?

 

4. Does this UEFI/Legacy bios support depend on the chip makers- Amd and Nvidia or does this support actually depend on the vendors? I mean if chip maker restricts a gpu to support only UEFI can the vendor, Evga or Sapphire be able to unrestrict it?

5. Is EFI bios is exactly same thing as UEFI? I saw some motherboard vendors (Gigabyte) mentioning EFI bios not UEFI.

 

6. Does this UEFI/Legacy only important for GPU? or is it crucial to check this support when buying SSD or other components as well?

7. What is asus AMI bios? that's Legacy bios right?