Hi there,

The result will be variable!

If intron allows to keep the reading frame between the 2 exons and no stop codon in the intron then final product will contain an insertion. If intron doesn't allow to respect the frame of the downstream exon then Cter frameshift of the protein will occur. If there is an in frame stop codon in the intron then product will be truncated compared to wt (with Cter sequence of the truncated product unrelated to wt protein sequence).

It depends. Non-sense mediated decay might target the mRNA for degradation. You might get a truncated protein product or a protein with a bunch of additional amino acids. Pull out an introductory molecular biology textbook - you'll at least learn the basics. The specifics are going to depend on the gene and the organism.