H1b Visa Stamp_DS160 and stamping related query

[sona02]

Hello,

I am looking to get H1b stamping as my current stamping expires this year in August (2022).

At US visa page (ais.usvisa) when I filled my info, it shows I am applicable for exemption from in-person visa appointment, which means I can send my document via mail for stamping. 

My question is:

1. I filled my DS160 number wrong, how can I change that with US embassy in Canada? Can I email them or is there a option on us visa page?

2. As my current stamping is valid until August, when can I send my documents to embassy for new stamping? I read somewhere that we can only apply up to 90 days before current stamping expires. Is that true?

 

Please help!