can i invest in more than one maxi ISA a year, as long as i don't open more than one a year?

Answer 1

The total amount each person can invest in Isas in one year is £7,000. This can be in one maxi Isa or two mini Isas,maxi Isa investments must be from a single provider. In any one tax year, you can contribute to one maxi Isa.
NO

Answer 2

No, your investment for any given financial year can only go into one maxi ISA. If you want to invest in two maxi ISA's around the same time then you could put money in one before 5 April next year and money in another after 5 April. This assumes you've not already used your ISA allowance for this tax year.