Not necessarily! If the person selling to you has owned the property for two years he can serve notice to extend the lease on the freeholder and assign the benefit of the notice to you in the sale contract and then you would not need to wait two years.
Extending your lease improves the value of your property and, subject to your status, the cheapest method of finance will usually be to take a further advance from your existing lender. You may also be able to borrow to cover the professional fees.
You are not able to buy the freehold of your flat or maisonette individually, but, if enough of your neighbours join you, it is possible to force the freeholder to sell. We can advise you on the details.
Unfortunately it is not possible to say and depends more or less on how reasonable the freeholder is. If agreement is reached quickly the process may take about a month but if no agreement can be negotiated and you have to go to the tribunal the process could take 6 to 12 months.