We aren't helping the poor person who asked the original question now but....
The no later provision is pretty common and when you get into the document and/or distribution policy it is pretty clear the sponsor gets to decide when the first election will be offered. Once the offer is made the employee then elects.
You seem to understand the installment provision correctly. Your example of a $266,000 balance is correct. The reason it says greater is because until you get to the very large balances you must pay within 5 years. So if an balance is $1,350,000 you would get 5 installments of $270,000 and that would be paid instead of the $265,000.
In the extreme if a person had for example a $10,000,000 balance you could pay $1,000,000 over 10 years. It meets the law and is greater than $265,000.