I want to visit the Wofo Temple, the Temple of Azure Clouds and the Botanical Garden.

Yes, it is feasible. They are not far from one to another. You can visit in this order:
The Temple of Azure Cloud - Botanical Garden - Wofo Temple
The former two are 2-3 miles, so you can take a taxi to reach or hike there. The distance to the Wofo Temple from the garden is around 2 miles.

Isn't the Wofosi temple inside the Plant Garden (the north-east end)?
How far is it between the Temple of Azure Clouds and the Wofosi temple?
It says you have to pay entrance fee at Xiangshan to get to the Temple of Azure Clouds. Is that true? Is it a long hike from there?
What part of the Garden would be the most beautiful to visit at this time?

Is everything open on Mondays?

Yes, the Wofosi is inside the garden. The distance Andy from Spain mentioned should be between different gates.

It is around 1.3mi from the Temple of Azure Cloud to the Wofosi. Some tourist would choose to walk between.

Yes, it is true that you cannot visit it unless you have the ticket of Xiangshan and the tickets for Xiangshan and the temple are separate ones.

Apart from Wofosi in the garden, you are recommended to see the chrysanthemum at this time. There will be a chrysanthemum exhibition on Sep. 26.

At last, the places you wanna visit are open on Mondays. Don't worry!