Yes – low heat treatment will not affect assay results.

This will depend on how the samples have been stored.  If samples are stored at 4°C, they should not be kept any longer than 2 days. You may conserve samples at -20ºC for long-term storage (for up to about 5 years), but be sure that recipients are well sealed to avoid evaporation. Avoid repeated freezing/thawing cycles (preferably no more than three).

Yes. Milk samples containing preservatives, such as Bronopol and sodium azide, may be used.

Please refer to the document Recommendations for milk testing
also available in French version Recommandations pour test sur échantillon de lait
also available in German version Empfehlungen für Milch
also available in Spanish version Recomendaciones para el análisis de leche
also available in Russian version Рекомендации для образцов молока