Can my brother from Australia buy a ticket from his credit card?
NO, your brother cannot buy an airline ticket from his credit card on your behalf. Bangladesh is listed on those countries which cannot use a credit/debit card to pay for someone else.
Pay on someone else's behalf
You can pay for another traveller's flight using cash. Just ...
Credit card fraud is a significant issue for airlines. See, for instance, this 2012 article:
Some of the travel agencies in the criminal underground are
full-service, pitching package deals that include airfare, car
rentals and even hotel stays. A hacker using the nickname “Yoshimo” on
one prominent fraudster forum offers “80-95 percent working ...
The Emirates Business and Marhaba lounges in Terminal 3 arrivals (level 1) are available to its arriving and departing passengers. Arrival hall signage points to where to get the shuttle bus that runs between Terminals 2 and 3.
Before takeoff or after landing, Emirates passengers can relax, refresh, and prepare for the next step in ...
Step 1. Get off the plane.
Step 2. Walk your way to the security / metal detectors
Step 3. Walk upto the transfer desk.
Step 4. You will be directed to a bus.
Step 5. Get on the bus.
Step 6. Travel to Terminal 2.
Step 7. Get off the bus.
Step 8. Proceed to your gate for FlyDubai
Step 9. Enjoy your flight.
You can stay in the airport transit area without a transit visa. There are airside hotels, so you do not necessarily need a visa at all. But if you want to pass immigration and enter Dubai, you can use this process:
Since you booked your flight with flydubai, you can apply for the 96-hour transit visa which lets you leave the airport and enter Dubai. You ...
The transfer between terminals may happen automatically for your hold luggage, but you will have to go to Concourse A apron level to take the bus from T3 to T2 in order to get yourself there.
The free showers are only in Terminal 3 Concourses B and C. There are only paid showers in Concourse A. If you have enough time to go to one of them to take a shower ...
Presuming you have an International->International connection in Dubai, the issue is not so much "security" as it is Immigration - you will be on one side of immigration, and your friends will be on the other side.
It will NOT be possible for your friends to pass through immigration to meet you (at least, not unless they happen to be departing from Dubai on ...
This is what Flydubai has on their website regarding the "OK to Fly" requirements. "When you've paid for your booking, you can contact a local Flydubai office or one of the Flydubai travel shops in UAE, India or Pakistan (depending on where your visa is being processed) for the approval. Nominal charges will apply. Operating hours for Flydubai local offices ...
You are eligible for a transit visa but you need a confirmed and paid round trip booking to request a visa via FlyDubai https://www.flydubai.com/en/plan/visas-and-passports/uae-visas You can apply on https://government.ae/en/information-and-services/visa-and-emirates-id/types-of-visa
Courtesy of Emirates web site sharing of the Timatic tool, the information used by airlines for passenger entry requirements (and as noted in the deleted @HankyPanky response), you would not require a visa (bold italic added emphasis mine):
Destination - United Arab Emirates (AE)
Passports and ...
The Dubai airports advice on transferring between terminals is:
Moving between terminals
When connecting between A, B or C Gates, all the gates are within walking distance. The only exceptions are the A Gates. For these you take the airport train.
If you are connecting to or from F Gates (located across the tarmac), your airline will tell you ...