The general rule is no players on loan at other clubs can't return and play for their parent club but there are some exceptions depending on the terms agreed.

In most cases, players on loan to other clubs are not eligible to play in the playoffs for their parent club. However, there are some exceptions, such as if the loan agreement specifies the player can return for postseason play or if a rule change permits it. Additionally, if a player is on a loan-to-purchase agreement, they may be eligible to play against their parent club in the playoffs.
Here's a more detailed explanation:
General Rule:
Loan players are typically ineligible to participate in their parent club's playoff matches. The loan agreement usually stipulates that the player's temporary transfer ends at the conclusion of the regular season.
Exceptions:
Loan Agreement: The loan agreement itself can specify whether the player is allowed to return for playoff games. If the agreement allows it, the player can be recalled to the parent club for postseason play.
Rule Changes: Some leagues or governing bodies have made rule changes that permit loan players to return for playoffs. For example, a change in 2018 allowed loan players to immediately feature for their parent club in additional matches like play-offs.
Loan-to-Purchase: If a loan agreement includes an option to purchase the player at the end of the loan, the player may be eligible to play against their parent club in the playoffs, especially if the loan club is not expected to keep them.
Recall Clauses:
Some loan agreements include recall clauses that allow the parent club to bring back a player at any time during the loan period. This can be a headache for loan clubs, but it's a common part of loan arrangements.