Dipak,
1. You won't be able to complete certain entries prior to the last day of the month, if that information includes a full month's info. For example, there are invoices we would receive from vendors after the last day of the month (because they include the entire month's activity), so I would have to wait to receive those invoices, then I would book the expense. If those invoices don't come in time for the month end cut-off, you would have to do an accrual for the expense. Now, if you know there are certain vendors that are always late with invoices, you could set up a monthly reversing accrual, and complete that before the end of the month, because it is just an estimate.
2. Yes, this goes along with #1. If the invoice isn't received for 2 months after the service, and accrual hasn't been made, you would have to record it in the period you received it, even though it was not for that period. If you were aware of the expense, you should've accrued for it 2 months ago.
3. The amount of days in their close, determines how many days they have to record entries (effecting their books) for that period. Let's say you have a 5 day close. You only have 5 days to close the books. If you get an invoice after day 5, it is too late to record the expense, and it will have to be recorded in the following month. That's why close can be very stressful at some places (my last job being one of them). We had a 5 day close, and a huge number of entries, and analysis to do before the end of day 5. I would actually try to get all the entries done by day 4, so I could use the last day of close to review my recs to see if there were any errors. If I found an error, I would still have time to correct it.
4. The most challenging this I faced at my last job were the tight month end deadlines. I had soooo many entries I had to complete (some required difficult analysis that could take up to 2 hours). So, when you are dealing with those types of entries, in that short amount of time, you open yourself up to simple mistakes, because you are just trying to go through them as fast as you can. If you make a mistake on one entry (depending on what type of entry it is), it could effect other entries, so you create more work for yourself in order to correct the mistake. There are also time where you have to wait on others in order to complete an entry, which again, sets you behind as far as deadlines.