Some companies list more than one stock (e.g. Sanofi has SAN, SNY, SAN,CHF...)
You will need to research that on a case-by-case basis. Some of it has to do with different classes of stocks, where others have to do with stocks being on different exchanges, and some of that has to do with listings in multiple countries. Related to dividend stock are a class of stocks known as preferred shares. They are like stocks, but also viewed to be very bond like as their yields are more secure.
In this case it looks like the symbols relate to the different international exchanges the stock is listed on.
Once I buy the stocks, how do I get the dividends? Are they paid automatically or I need to make a request to the company?
This will depend a bit upon who you buy the stock from, but there are two dates that are important to this. The first is the ex-dividend date, which is that date that you must own the stock before to get the next dividend. The other date is the payment date which tends to be about a month later, YMMV.
In a traditional broker the money appears on the payment date. If you use a Dividend Reinvestment Plan (DRIP) then frequently your dividends will buy more shares of the same stock. Some brokers allow your dividends to be reinvested and this tends to be the default for mutual funds. With mutual funds it is allowed to own fractional shares where this is not always allowed with stocks. For example, if your dividend payout is $10, but a share of stock is $30, it is only enough to buy .3333 of a share, provided there are no commissions.
In the case of DRIPs or mutual funds, you can frequently select for the dividends be transferred to you, including deposited to your checking account.
Editorially, I would recommend against single stocks unless you have a lot of money to invest. There are ETFs like DGRO that focus on dividend paying stocks, and PFF that focus on preferred stocks. Many brokers offer these ETFs purchased without commission. Additionally, a S&P500 index fund will also pay dividends.