Bloons TD 5

Random Missions are accessed from the Challenges menu. Within the menu you can choose from 9 missions and they're randomized every time you access the menu. You have the chance to replay a random mission after you've finished it successfully but only if you don't exit the screen. Once the available missions are randomized again you can only start replaying already finished missions once you have less than nine unfinished missions. When you've finished all random missions you're always presented with nine already finished missions so if you want to play a specific mission you will probably have to enter and exit the mission screen multiple times. The chances are roughly 4% each time for the mission you desire to play to appear.

A little bit of history:

Random Missions were originally designed for the web browser version of Bloons TD 5 and were released as daily challenges but most of them were suggestions from the community. Sometimes mission descriptions talk about left and right monkeys. This is because the tower menu originally only had two columns, compared to the 3 it has now but it's hard to tell which monkey is from the left and which from the right side. Some missions are not as challenging as intended because of the added bonuses e.g. more starting lives and reduced cooldowns. Most Random Missions take place on very few maps only, the majority of the maps is excluded which can make progress on this trophy a bit boring after a while. Some of these Random Missions were easy by nature but others were challenging and a few were extremely hard in the original game but the introduction of Double Cash and global attributes e.g. increased Popping Power, Attack Speed and reduced Zeppelin health, they are now very easy. If you want to experience a challenge then you can deactivate all bonuses in the Monkey Lab.

If you struggle with any random missions even with Double Cash on, remember that you can set a speciality building and remember that in some missions you're allowed to use agents. You have to purchase an average of 40-45 agents of each type anyway so use them when you need them. The most annoying missions were the one on castle map where you could use only road spikes and pineapples, and three missions where you're limited to only one type of tower. For the castle map, just place two Tribal Turtle agents at the entrance and set them to last. It will be a cakewalk now because they will destroy all Leads so you don't have to aim with pineapples. Pay attention to the RBE at the start of each wave and you'll have an idea how many road spikes to place.

The other three annoying missions limit you to:

Dart Monkeys
Boomerang Throwers
Monkey Apprentices.

The Towers for the Boomerang Throwers and Monkey Apprentices are also limited to 2/2 so you really have to fill the map with lots of towers. This isn't difficult but activating the respective Speciality Building will make your towers more powerful and the task less tedious.