Bit sad to see nobody helping, let me try:
Yes, of course.1) is it possible to undertake more than one contracts?
Yes.2) is it better to undertake them as sole trader or PAYE or LTD?
Absolutely.3) will I earn as much as I would as permanent employee or I will pay more tax etc?
No, it'll be fine.4) if I take them as permanent employee arranging with the employers to have flexibility in completing the work later in the evening, will there be a problem?