By that extension, <Beautiful Technique> SIGNI under the protection of Contempora's second [Constant] ability that are marked by Charms cannot use their [Action] abilities due to Arachne Pider's second [Constant] ability.
If you have Arachne Pider in play and your opponent plays Code Labyrinth Louvre in front of Arachne Pider, Louvre is not marked with a Charm because Arachne Pider will have lost her abilities already due to Louvre's [Constant] ability.
Your opponent cannot "choose not to select" a 1 of their SIGNI marked with a Charm for Arachne Pider's third [Constant] ability.
All Resona are attached with a Charm as per Arachne Pider's first [Constant] ability. You (the owner of Arachne Pider) may choose which of the Arachne Pider's abilities will resolve and apply the Charm first.
The resolving Arachne Pider ends prematurely because your opponent only has 1 card remaining, applying only 1 Charm before initiating refresh.
The second Arachne Pider will then be able to activate, attaching the last Charm.
If both players have only 1 Arachne Pider on their respective sides of the field attached with a Charm, and the turn player enters Attack Phase: the turn player has priority in activating Arachne Pider's third [Constant] ability, causing the non-turn player's Arachne Pider to be banished and being unable to activate her own third [Constant] ability.
If you have Arachne Pider in play during your opponent's turn, and your opponent plays Rabiel, Protector of Holy Arts and selects Arachne Pider for Rabiel's [On-Play] ability: the turn player (your opponent) has priority in resolving their effects, causing Arachne Pider to be sent back to your hand (or in this case, the LRIG Deck).
Because Arachne Pider's place of trigger (field) no longer matches her place of activation (hand /LRIG Deck), her first [Constant] does not attach a Charm to Rabiel.
If your opponent puts Rabiel into play during your turn, for example your opponent using Soap Summon's ability to put your opponent's Rabiel into play from your opponent's hand during your opponent's ARTS step, Arachne Pider's ability takes effect first, and a charm is attached to Rabiel. Your opponent may then pay Rabiel's cost to send Arachne Pider to your hand (or in this case, your LRIG deck).