multi session cd writing

1. In ver 8 micro, there is no provision to select single or multisession. Does it mean that by default is automatically in multisession?

2. What is the major improvement between ver 6 and ver 8.

3. under what circumstances, the sessions 2 and beyond are not readable? I have come across an instance once with CDburner XP pro. What precautions one should take to avoid this?

Thanks.

 

I use nero burning rom 6.6.1.7...multisession works fine with that