It's a bit strange, as virat sounds like a name, so should be capitalised. Backing here refers to gambling - he is metaphorically putting a bet on Virat. 'Come good' is somewhat poor English, and means 'turn out well'. The whole thing looks like a British newspaper sports headline, and they are somewhat notorious for not being grammatically strict (and that's being generous) So - Chris is betting that Virat will do well in England. It could be purely metaphorical, as in he just believes that he will get better. It could be a bit more practical gambling-wise if Chris has employed Virat to do a job for him.

This sentence you have provided does not really make sense. However, the use of "backs" in reference to another person can be in reference to a show of support. For example, "I will never respect my senator again after I found out he backed Trump". It is similar to the idea of having someone's back - meaning you support them and will watch out for them.

Sentence has 3 E's and no A. There is no capital on Explain either, but you should use one on England.