What is the ruling on the prayer of one who suspected the discharge of urine during prayer and later found its traces, and is it obligatory to repeat the prayer after an incorrect purification of clothes? And what is the ruling on slight yellowness that appears on clothes near the posterior after purification?

If you doubt during prayer whether a drop of urine has fallen or whether your ablution (wudu) is valid, then your prayer is sound, and there is no need to interrupt it or inspect your garment or private parts. The default assumption is the validity of worship until there is proof to invalidate it.

However, if you are certain that urine has indeed exited, then you must purify yourself, renew your ablution, and cleanse anything affected by the urine with purifying water until the trace of impurity is completely removed. Doubt concerning the exit of urine has no effect on the validity of prayer or purity. Unless it is certain that it is urine, it holds no ruling. A yellow color on the garment does not affect purity unless it is certain that it is a trace of feces.