1. On July 1, 215 Corp. borrowed funds from a bank by signing a long-term note. Repayment is at the option of the borrower but interest will accrue on the unpaid balance. Interest will be determined at year-end
2.Purchased stock as a long-term investment in another company (This is an investing cash flow)
3.The stock purchased in event 2 is sold for cash
4. Existing owners purchased additional shares of stock in this company

Is it correct:
1. Dr Cash xxx
Cr Notes Payable xxx

2.Dr Long-term Investments xxx
Cr Cash xxx

3. Dr Cash xxx
Cr Common Stock xxx
Cr gain on sale of investments

4.Dr Common Stock xxx
Cr Cash xxx

Thank you!

1 and 2 are good.

In 3, remember that you're selling the asset bought in Event 2. Hence the credit should reflect that particular asset.

Also in 3, I don't see any basis for assuming the asset was sold at a gain. It might be better to indicate in the entry that it's a credit to Gain or a debit to Loss.

In 4, remember that cash in coming in to the company, as a result of the transaction.