Maybe but you can't be certain. The problem is not whether the codons are maximally optimized for the mammalian cells, but rather do you have some problem codons (codons that are rarely used). These rare codons are generally the main problem. So scan your sequence assessing codon usage for mammals and see whether most or all of the codons are at least middle or above in usage.

That will likely work with somewhat reduced yield. But it's probably not something you want or need to be doing in the age of gene synthesis.

You can provided that it is expresses from mammalian expression promoter. You can't express T7/Lac promoter in mammalian cells. You need to clone same DNA seq in mammalian expression plasmid and it should work.

The DNA sequence optimized for expression in E. coli may not necessarily work effectively for expression in mammalian cell lines. This is because the genetic and regulatory mechanisms in bacteria, such as E. coli, differ significantly from those in mammalian cells.

Here are some key considerations:

Considering these factors, it is generally recommended to design and optimize DNA sequences specifically for expression in mammalian cell lines if your goal is to achieve efficient and functional protein expression in those cells. This may involve selecting appropriate promoter regions, codon optimization for mammalian usage, and incorporating necessary regulatory elements