No, janeu is not worn in marriage by all sects – and it is not a Jain religious practice at all.

In simple terms:

• Janeu (yajnopavit) is a Hindu sacred thread, linked to the Upanayana (thread ceremony) and certain Hindu castes/traditions.
• In Jain Dharma, there is no scriptural requirement or tradition of wearing janeu, either in:

- childhood/initiations, or - marriage rituals.

Among Jain sects

• Digambar Jains – no janeu as a Jain religious practice, including at marriage.
• Shvetambar Jains – also no janeu as a Jain religious practice, including at marriage.

In some regions, a few Jain families may follow local Hindu-style customs at weddings (like certain threads or symbolic items), but:

• These are social/cultural practices,
• Not prescribed by Jain Agams or Jain Acharyas as part of Jain dharma,
• And they can vary from family to family.

So, if your question is:

• “Do all Jain sects wear janeu in marriage?” – No, none of the Jain sects have janeu as a religious requirement.
• If you meant Hindu sects/castes in detail – that goes beyond Jain-dharma scope.