Simulate a data frame with different sequence per column [closed]

Question

I would like to simulate in R a data frame with 4 columns with the above conditions:

1. Each row is summing up to 1

2. The first element of column 1 starts with being closer to 1, say 0.9, but gradually decreases per row.

3. The elements of the other 3 columns start low, say something between 0.02 - 0.05, but gradually increase with each row.

4. I would like the last row of the data frame being c(0.25, 0.25, 0.25, 0.25).

Can you help me with creating something like that ? Thank you in advance!